Electrophysiological and neuroanatomical studies are proposed to investigate the cells of origin and the post-synaptic effects of retinal afferents terminating in brain stem areas implicated in eye movements. Preliminary data indicate that neurons in the dorsal raphe nucleus receive axons from Y ganglion cells and that neurons in the nucleus centralis superior receive both Y and W cell axons. In addition, the nucleus prepositus hypoglossus and the nucleus reticularis pontis oralis receive retinal afferents of undetermined origin. Experiments are proposed to further investigate these findings. Utilizing techniques based on retrograde transport, in separate studies, the enzyme horseradish peroxidase (HRP) will be iontophoretically applied to each of the above structures and the retinas examined to determine the size and location of ganglion cells involved. Physiological investigation is proposed to record unit activity in the retina and brain stem nuclei. A series of studies is designed to functionally identify retinal ganglion cells projecting to the brain stem by examining their receptive field characteristics and the conduction velocity of their axons as a function of electrical stimulation. Recordings of brain stem units will be performed in conjunction with visual and electrical stimulation of the optic pathway. The organization of their receptive fields, i.e., binocularity of input, movement sensitivity and optimal stimulus configuration will be determined. Latency of response to electrical stimulation of optic afferents and visual structures will be ascertained to provide evidence of direct and indirect visual input. Intracellular recording of brain stem units with HRP-filled electrodes will document the kinds of post-synaptic potentials resulting from stimulation and illustrate morphological differences among these target neurons.